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Questions tagged [parton]

A parton is a gluon, quark or antiquark in the eponymous model of scattering involving hadrons. In the hadron's infinite-momentum frame, incoming particles will be scattered instantaneously and incoherently, reducing the problem to a simple kernel convolved with parton distributions, at a particular physical scale (as probed by the inverse of the momentum transfer).

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Parton distribution function in terms of Fock space kets

To my understanding, I can (at least, formally) express the (unnormalized) PDF for a certain constituent of a composite state as $$ f(x)=f\left(\dfrac{k}{K}\right)=\sum_j m_j^{(k)}|\langle\psi_j^{(k)}|...
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Question about DGLAP evolution equation

I am reading chapter 32.2 of Schwartz's QFT book, where he defines the renormalized PDFs $f_i(x, \mu)$. This leads to an equation (32.48), which relates PDFs at different scales $\mu, \mu_1$: $f_i(x,\...
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Integration of the splitting function

I have a problem performing the following integration provided in the paper by Catani and Seymour (arXiv: hep-ph/9605323) page 27. Given is the integral $$ \mathcal{V}=\int_0^1 (z(1-z))^{-\epsilon} \...
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How to derive operator form of the parton distribution function

A similar question is found here in Stackexchange a year ago without any response. I am following the formulation of the parton densities from the handbag diagram in Collins Handbook of Perturbative ...
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Computing hadronic cross sections with PDFs

I am trying to estimate the cross section for a BSM process at the LHC, and I would like to ask if anyone knows what is the simplest way to integrate over the PDFs, for example with Mathematica. I ...
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Parton model and impulse approximation for the process $2\to 1$

Consider a process $$ \tag 1 N+N\to X+\text{all}, $$ where $N$ are nucleons and $X$ is some massive particle. Assuming the parton model is valid and there is vertex $PP'X$, where $P,P'$ are partons ...
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Applicability of parton model at low factorization scale

Consider scattering process at partonic level occuring at low factorization scale $\mu^{2}\lesssim 1\text{ GeV}^{2}$ (for example, with the "hard" process $2\to 1$ with low mass produced particle, ...
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Shape of partons from differential cross section as function of $Q^2$: is it valid, despite the $\theta$ dependence?

For deep inelastic scattering of electron on a nucleon the following graph represent the ratio $$\frac{\frac{d^2 \sigma}{d \Omega d E'}}{(\frac{d \sigma}{d \Omega})|_{Mott}} $$ as a function of $Q^2$,...
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Parton model: relation between $F_2(x)$ at fixed $Q^2$ and differential cross section as function of $x$

Consider deep inelastic scattering of electron on proton and parton model: $F_2(x)$ as a function of Bjorken $x$ at fixed $Q^2$ goes as in the following graph. The differential cross section is: $$\...
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Deep Inelastic Scattering cross section: Smearing of the $F_2(x)$ graph and relation of form factors with Fourier Trasform of nucleon distibutions

Consider Deep Inelastic Scattering cross section $$\frac{d^2 \sigma}{d \Omega d \nu}=(\frac{d \sigma}{d \Omega})|_{Mott} \{ W_2(Q^2,\nu)+2 W_1(Q^2,\nu) \tan^2(\theta/2) \}$$ It is said that the ...
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Drell-Yan process and factorization scale

What is the most relevant choice for the factorization scale of the Drell-Yan process? Can it be the invariant mass at the reaction threshold?
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Computing the $p_{T}$ spectrum of hadrons in pp collisions by knowing the $p_{T}$ spectrum of quarks

Consider the differential quark production cross-section $d\sigma_{pp \to q\bar{q}}/d|\mathbf{p}_{T}|$, where $|\mathbf p_{T}|$ is the momentum transverse to the $pp$ beam line. Next, assume that the ...
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Bjorken Scaling and the Parton Model

It is often said that Bjorken scaling of the deep inelastic structure functions \begin{equation} \nu W_2(\nu ,Q^2)\rightarrow F(x) \end{equation} (where $Q^2$ is the virtuality of the photon, $\nu=\...
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Parton distribution function and factorization scale

Consider some deep inelastic scattering $y f\to y f$, where $f$ is a parton inside a nucleon $N$, and $y$ is some particle. The cross-section is then $$ \sigma_{\text{DIS}} = \int dx f_{N/f}(x,Q^{2})\...
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Leading order DGLAP evolution

Consider the leading-order (LO) DGLAP ((Dokshitzer–Gribov–Lipatov–Altarelli–Parisi) equation $$x \mu^2 \frac{d xg(x,\mu^2)}{d\mu^2}= \alpha_s \int_x^1 dz P_{gg}(z) \frac{x}{z} g(\frac{x}{z}, \mu^2) + \...
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Parton model in experimental particle physics

In experimental particle physics, what does "parton-level" , "particle-level" and "detector-level" exactly mean ? PS : detailed explanations, links, etc .. would be deeply appreciated
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Parton distribution function - dependence on $Q$?

In one of my previous questions I define the parton distribution function, following that of D.Stump as follows: $f_i(x,Q^2)dx$ is the mean number of the $i$th type of patron with longitudinal ...
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Do electrons interact with gluons?

I know the straightforward answer to this question is no: electrons are leptons which by definition don't interact via the strong force, gluons are the mediators of the strong force and hence ...
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Sea quark parton annihilation?

Consider the figure below1: This can be read as follows (please correct me if I am wrong): two particles come in and 'fragment', a parton from each particle $C$ and $D$ annihilate to form the ...
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Towards a matrix element definition of PDF

In Schwartz's book, 'Quantum Field Theory and the Standard Model' P.$696$, he starts to derive an expression for a parton distribution function in terms of matrix elements evaluated on the lightcone. ...
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Spin-charge separation and Spin-Statistics relations

Usually, we associate the half-integer spin to fermion, and the integer spin to boson. And there are constraints like the Spin-Statistics relations. However, in Spin–charge separation or the parton-...